Specific reagents will be prepared to each of the major components of the primate type C viruses to use to study their evolutionary relationship and the extent of expression of virus specific imformation in normal humans and in humans with tumors, especially leukemias and lymphomas. To define the level at which cells prevent the expresion of endogenous virus information and to determine where in the cell the virus information physically resides. To develop techniques that utilize radiation, chemical carcinogens, and viruses to produce human cell transformation and/or activation of type C virus in tissue culture. To characterize the biology and immunology of the endogenous and infectious type C viruses of each of the mammalian species from which viruses have been or will be isolated. In order to determine their relationship to one another and to the normal cellular genes.